Gas safety valves are usually used in gas distribution systems to safely avoid gas leakage, and possible ensuing damage, in case of incorrect handling.
Such safety valves have a ball shutter and a control rotation member in form of a knob with one or two gripping fins, or a lever or the like, where solely the representative term of a knob will be used hereinafter for the sake of simplicity. Such knobs are generally rotatable for a ninety-degree rotation to rotate the ball shutter from the opening position to the closing position and vice versa.
Gas safety valves are known in different embodiments, which provide for a control with a double manoeuvre, as required for example in the United States for the so-called latching-type valves.
A valve of this type is disclosed, for example, in documents IT-A-1.346.153 and U.S. Pat. No. 7,178,781 B2 on behalf of the Italian company Valvosanitaria Bugatti S.p.A.
These known valves have the common characteristic of requiring various additional components with respect to the conventional valves and provide for a double control manoeuvre comprising, starting from the valve in closed position, a first axial movement of lowering the knob countering a spring and the subsequent rotation of the knob by 90° to take the knob/shutter to the opening position.
It is clear that, considering the brief rotation for opening the valve by 90°, the only guarantee of safety against inadvertent opening is provided by the compression pressing on the knob, which actually may also be caused inadvertently for various reasons both by the installers, users, other people or household animals. In a known case of opening a safety valve of this type was actually caused by a dog which lay on the knob pressing it with its weight and then rotating it by rubbing it with the movement thereof.
Furthermore, such known safety valves are not capable of equally providing a safety of a shutter in opening position, as required at times, hence they cannot exclude inadvertent partial or full closing movements of the valve.